The present invention relates to a hand-operated cable cutter capable of easily cutting off wire ropes, electric wires, communications lines, reinforced bars or other metallic cables.
For example, U.S. Pat. No. 4,223,439 discloses a cable cutter of this type. The conventional cable cutter comprises a stationary handle and a movable handle which are joined together at their respective upper portions and biased in a direction of one away from the other by a spring, a stationary blade having the base portion thereof fixed to the upper portion of the stationary handle, a rotary blade having the base portion thereof attached pivotally to the leading end of the stationary blade and also having the outer arcuate side surface formed with continuous teeth, and an operation lever pivotally attached to the upper portion of the movable handle and provided with an engaging claw for engagement with the teeth of the rotary blade, whereby the opening and closing operation of the movable handle relative to the stationary handle moves the operation lever to rotate the rotary blade having the teeth thereof kept in engagement with the engaging claw in the closing direction, i.e. in the direction of cutting a cable or the like.
In actual use of the conventional cable cutter, a cable or the like is placed in a space defined by the stationary blade and the rotary blade, then the free end of the rotary blade is rotated about the pivot to be guided in the closing direction, thereby surrounding the outer periphery of the cable or the like by the stationary and rotary blades, and thereafter the movable handle is continuously operated to alternately close and open relative to the stationary handle. By effecting the continuous operation of the movable handle, which causes the engaging claw of the operation lever to repeat its action of idly sliding over one of the teeth and engaging with the adjacent one of the teeth, until the aforementioned space becomes zero, the cable or the like can be cut off with the opposed cutting edges of the stationary and rotary blades.
In the conventional cable cutter, the base portion of the rotary blade is pivotally attached to the upper portion of the stationary blade. In other words, the pivot portion for the two blades is located at the uppermost position of the cable cutter. Since this construction makes it possible to cut off a cable or the like in the state of being completely surrounded by the two blades, the conventional cable cutter can advantageously be used in cutting off cables of a relatively large diameter. Further, when attention is paid only to the cable cutting operation of moving the rotary blade in the closing direction in conjunction with the opening and closing operation of the moveable handle, the conventional cable cutter utilizes the operation lever pivotally attached to the moveable handle as means for moving the rotary blade in the closing direction. This operation lever constitutes a so-called toggle mechanism in cooperation with the place where the two blades are pivotally attached to each other and the place where the two handles are joined together. The adoption of the toggle mechanism has a merit in that a small force can give a large shearing force to the rotary blade, whereas it has a demerit in that it is impossible to move the rotary blade in the opening direction during the cable cutting operation.
Depending on the relationship between the cutting ability of a cable cutter and the hardness and diameter of a cable to be cut off, after the cutting edges have bitten into the cable, there has been a fair possibility of the rotary blade being incapable of rotating in the closing direction even by repeatedly operating the movable handle. However, none of the conventional cable cutters has a structure capable of easily solve such an accidental problem, i.e. a structure for forcibly moving the rotary blade in the opening direction and easily removing the cable. This is the most significant problem in using the conventional cable cutters. Some of the conventional cable cutters have a mechanism for releasing the engagement between the engaging claw of the operation lever and the teeth of the rotary blade. However, this releasing mechanism functions not as means for forcibly moving the rotary blade in the opening direction during the cable cutting operation, but as means for moving in the opening direction the rotary blade kept only in the state after the termination of or before the beginning of the cable cutting operation. For this reason, in the case where such an accident as described above arises, i.e. where the cutting edge of the rotary blade has bitten deeply into the cable, even though the engaging claw of the operation lever can be brought to a state of disengaging from the teeth, it is impossible to rotate the rotary blade in the opening direction only with the force of the hand and, what is worse, dangerous work is required in such a rotating operation.